This invention relates to a polyolefin composition from which films may be prepared having the stiffness, opacity and printability normally associated with paper. In another aspect, the present invention is directed to polymeric sheets or films of such polyolefin compositions useful in the field of photography as, for instance, in the preparation of photographic elements and to photographic elements employing such sheets.
Although polymeric films which can be printed are known, they have not proved entirely satisfactory as replacements for paper. One drawback of these polymeric films has been their lack of stiffness and opacity. Another deficiency of prior art printable polymeric films is their instability. For example, British Patent No. 1,090,059 describes a printable polymeric sheet of polyethylene-based compositions in which siliceous fillers are incorporated along with a resin such as an ethylene-vinyl acetate copolymer. Other polymeric sheets have been proposed as paper substitutes made from polyvinyl chloride, polyethylene, polystyrene, and polyamide. Although sheets of these polymeric compositions exhibit many of the characteristics normally associated with paper, the sheets have been found to be labile to heat and ultraviolet light and, in addition, are degraded by certain adhesives (e.g., animal glues containing permanent plasticizers) used in book casing and poster-board fabrication or are subject to yellowing.
Some sheets are made by synthetic fibers formed on a paper making machine. Others require special surface treatments such as solvent degradation to obtain a white appearance or adherence to subsequent coatings or to a printed image.
Polymeric sheets have also been proposed as substitutes for paper in the preparation of photographic elements containing the sheets as supports for one or more light-sensitive layers. These polymeric materials, however, have yet to display the outstanding advantages of paper or similar fibrous materials. Among the shortcomings of polymeric photographic supports are difficulties such as dimensional stability, i.e. the occurrence of dishing, fluting and edge penetration, photographic activity of components resulting in fogging, etc. In addition, major losses in sharpness occur due to the separation of the lightsensitive layers from the reflecting layers adjacent the polymeric sheets.
One object of the invention, therefore, is to provide polyolefin compositions capable of being formed into films and sheets which possess characteristics usually associated with paper as, for instance, stiffness, preferably having a Tensile Modulus of elasticity of above about 50,000, opacity and printability; yet retain the desirable properties of polymeric film such as high tear strength, high elongation, water-resistance, heat sealability, extrudability, ability to be laminated, etc.
Another object of the invention is to provide polymeric compositions capable of being formed into sheets having the desirable properties of the paper and polymeric films, yet of improved stability to ultraviolet light and heat of from about 400.degree. to 500.degree.F.
Yet another object of the invention is to provide photographic elements comprised of at least one radiation-sensitive layer on a photographically inert polymeric support which exhibit improved image sharpness and dimensional stability while, at the same time, exhibiting high resistance to water, temperature, wear-and-tear and abrasion.
A further object of the invention is to provide elements of the above type wherein the radiation-sensitive layers are silver halide emulsion layers.
Yet a further object of the invention is to provide photographic elements of the above type wherein the photographic support is coated with silver halide emulsion layers differentially sensitized to blue, green and red.
A still further object of the invention is to provide multilayer elements coated on said polymeric support wherein the silver halide emulsion layers contain color-forming couplers therein.
An additional object of the invention is the use of the polymeric materials as receiving sheets in diffusion transfer photographic processes.